Classroom-based continuous assessment (CA) has become an important component of Namibia's post-independence emphasis on learner-centred education. This paper compares continuous assessment results with end-of-year examination marks for Grade 10 Mathematics for the years 2008-2010. Against this backdrop, and given that classroom-based continuous assessment contributes 35% to the Grade 10 promotional mark for Mathematics, the paper then interrogates teachers' views of the importance and role of classroom-based continuous assessment. A comparison of average CA and end-of-year examination marks for 62 Junior Secondary schools in the Oshikoto region of Namibia for the years 2008-2010 shows that the dominant trend over this 3-year period was an average CA mark that was notably lower than the average end-of-year examination mark, all three years showing a weak correlation between average CA and end-of-year examination marks. An analysis of the interview data from three principals and 15 mathematics teachers suggests that while the use of continuous assessment is generally valued in terms of its potential to inform the teaching and learning process, use of classroom-based continuous assessment as a component of the Grade 10 promotional mark has given rise to tensions between the summative and formative purposes of CA. More specifically, there is evidence to suggest that the inclusion of a CA component in the promotional mark may be emphasising summative aspects of CA to the detriment of its formative value.